The present invention relates generally to high performance arc heaters, and more specifically to a segmented arc heater which uses dual toroidal electrodes.
Arcs and arc processes have been used since the turn of the century in a myriad of applications ranging from welding to chemical synthesis. With the advent of the missile and space age, a need became apparent for a method of producing reentry conditions in the laboratory in order to investigate the many phenomena that missiles and spacecraft encounter as they travel back to earth. The effort to produce these conditions has led to the development of large arc heaters and plasma jets which can be controlled to give the parameters desired. Small, compact and low power arc jet thrustors have also been developed, as well as small cutting and welding arc torches and high intensity light sources.
High enthalpy ablation tests have achieved air enthalpies of the order of 3000 Btu/lb at 250 atm pressure. The primary limitations to further increases in enthalpy have been arc control, electrode (anode) erosion, and arc radiation loss. The task of reducing electrode erosion in arc heaters is alleviated, to some extent, by the systems disclosed in the following references, the disclosures of which are specifically incorporated herein by reference; U.S. Pat. No. 4,242,532 issued to J. Squibbs; and a technical article by J. E. Harry et al, entitled "Simultaneous Operation of Electric Arcs From The Same Supply," IEEE. Vol. PS-9, No. 4, Dec. 1981.
The Squibbs patent discloses a state-of-the-art electric arc furnace augmented with a method of controlling exhaust gas emissions. While it is an instructive disclosure, it is believed that the electrodes would remain subject to conventional erosion.
The work of J. E. Harry and R. Knight on "Simultaneous Operation of Electric Arcs from the Same Supply" was found to have application to the present concerns. Their results showed that two separate parallel arcs could be maintained from a common power supply by using individual stabilizing resistors for each arc. Three-root discharges (two anodes and one cathode) were produced when separate arcs were coalesced. Their tests showed that series resistors stabilized each arc adjacent to the electrode to which the resistor was connected and one of the separate arc roots to the cathode was extinguished. The arcs involved in their tests were at low power and atmospheric pressure.
In view of the foregoing, it is apparent that there currently remains a need to reduce electrode erosion and increase arc control in arc heaters in high performance applications. The present invention is intended to satisfy that need.